Meningitis is a clinical condition involving inflammation (swelling) of the protective membranes around the brain and spinal cord (meninges).
Meningitis is mainly due to a bacterial or viral infection of the fluid that surrounds the brain and spinal cord. It can also occur due to certain injuries, cancer, certain drugs, or other kinds of infections.
Infection and inflammation around the brain and spinal cord can result in the activation of the immune system leading to inflammation and a wide range of symptoms such as fever, headache, seizures, brain damage, stroke or even death.
The incidence of acute bacterial meningitis is five cases per 100,000 adults per year in developed countries and maybe 10 times higher in less developed countries.
Pathophysiology
The reasons behind meningitis include infections caused by the bacteria, virus, fungi or other parasites. Other important risk factors include environmental exposures (such as a parasite), recent travel, or an immunocompromised state such as having HIV, diabetes or undergoing chemotherapy treatment.
Non-infectious causes of this disease include autoimmune or rheumatological diseases and certain medications. Bacterial meningitis can be caused by bacteria such as Streptococcus pneumonia (pneumococcal meningitis), Neisseria meningitides (Meningococcal meningitis), Haemophilus influenza (Haemophilus influenza meningitis).
Viral meningitis is caused by enteroviruses (a virus that enters the body via mouth and travels to the brain and surrounding tissues, where it multiplies), varicella zoster virus, influenza, mumps, and HIV. Fungal meningitis is most commonly caused by a fungus Cryptococcus neoformans. Parasitic meningitis is caused by cysticercosis (a tapeworm infection in the brain). Sometimes, meningitis is non-infectious and is caused by cancers, lupus, certain medications, head injury and brain surgery.
Symptoms
Bacterial meningitis can be identified by the classic trio of symptoms of fever, headache and neck stiffness.
Other symptoms of meningitis include:
- Nausea
- Vomiting
- Photophobia
- Sleepiness
- Confusion
- Irritability
- Delirium
- Double vision
- Coma
- Fatigue
- Muscles pain
- Anorexia
- Sensitivity to bright light
The history of the patient should also address the following:
- Exposure to patients or animals with similar illness
- Previous medical history and treatment medications
- Geographic location and travel history
- Season and temperature
- Factors controlling incidence, distribution of disease
- Factors which increase susceptibility to this disease
Symptoms of viral meningitis are common to all kinds of causative agents. Enteroviral infection can be detected by widespread rashes, symptoms of inflammation of fluid around the heart and lungs, conjunctivitis, severe pain in muscles between the ribs or diaphragm, mouth blisters, and hand-foot-and-mouth disease. Important signs to watch for an infant include fever, lethargy, not waking up for feedings, vomiting, stiff body, unusual irritability and a full or bulging fontanel (the soft spot on the top of the head).
In order to assess the disease, the examination should include for signs of lymphadenopathy (a disease of lymph nodes), papilledema (increased pressure in or around the brain that causes optic nerve to swell), dysfunction of cranial nerves or other neurological focal signs.
Diagnosis
After a physician completes a physical examination and evaluates the medical history, the doctor may advise the patient to undergo certain tests to confirm the presence of infection or inflammation. It is important that the diagnosis is made in an early stage as symptoms can appear suddenly and escalate to brain damage, hearing or speech loss, blindness and even death.
The diagnostic tests for meningitis include:
- A neurological examination to assess motor and sensory functions, nerve function, hearing and speech, vision, coordination and balance, mental status, changes in mood or behavior.
- Laboratory testing of blood, urine and body secretions to help in identifying brain and spinal cord infections
- Identification of the causative organism
- Complete blood count tests (CBC)
- Serum electrolytes
- Serum glucose
- Blood urea nitrogen (BUN) or creatinine and liver profile
Some additional tests may include:
- Blood, nasopharynx, respiratory secretion or skin lesion cultures
- Syphilis (a sexually transmitted disorder) testing
- Serum prolactin testing
- Lumbar puncture and analysis of cerebrospinal fluid
- Neuroimaging (CT scan of head or MRI of the brain)
- Electroencephalography, or EEG to identify abnormal brain waves by monitoring the normal activity of the brain by non-invasive methods.
Treatment
It is important to treat complications of acute meningitis such as hypotension or shock, low levels of oxygen in the blood, low levels of sodium in the blood, altered mental status, seizures, abnormal heartbeats, stroke and worsening of chronic diseases.
Early treatment of meningitis involves the use of antibiotics that can cross blood-brain barrier depending on the patient’s age and condition. Appropriate treatment with antibiotics can greatly reduce the risk of fatalities from this disease.
Anticonvulsants are prescribed to prevent seizures and corticosteroids are given to reduce inflammation in the brain. Infected sinuses may need to be drained. Corticosteroids such as prednisone can be used to relieve pressure in the brain and swelling as well as to prevent loss of hearing. Antibiotics developed to kill bacteria are not effective against viral meningitis. However, most of the cases of viral meningitis are benign and self-limited and are rarely life-threatening. If needed, specific antiviral therapy may be used for treating viral meningitis.
Fungal meningitis is treated with intravenous fungal medications.
Other types of meningitis are treated with specific therapy as considered appropriate for the causative organism:
- Fungal meningitis treated most commonly with amphotericin B, flucytosine, fluconazole, itraconazole
- Tuberculosis meningitis is treated with isoniazid, pyrazinamide, ethambutol, streptomycin, rifampin
Prevention
It is important for people to avoid sharing food, utensils, glasses and other objects with a person who may have been exposed to or have this infection. People should always wash their hands often with soap and warm water.
Effective vaccinations are available to prevent Haemophilus influenzae, pneumococcal and meningococcal meningitis. People who work or live with someone who has been diagnosed with bacterial meningitis may be asked to take antibiotics as a preventive measure for a few days. People should also limit their outdoor activities or wear long-sleeved clothing to avoid bitten by an infected mosquito.
References:
- Heckenberg SG, Brouwer MC, van de Beek D. Bacterial meningitis. Handb Clin Neurol. 2014;121: 1361-75.
- Rodrigo Hasbun, MD. Meningitis. https://emedicine.medscape.com/article/232915-overview
- Centers For Disease Control and Prevention. Meningitis. https://www.cdc.gov/meningitis/viral.html
- Meningitis and Encephalitis Fact Sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Meningitis-and-Encephalitis-Fact-Sheet
